Liquid cooling system

ABSTRACT

A liquid cooling system includes a heat-radiating sheet having a pair of heat-conductive metal plates that are superimposed on each other, and having a circulating flow passage between the pair of heat-conductive metal plates; a plurality of heat-receiving areas partitioned on the heat-radiating sheet; a plurality of heat-generating elements installed on each of the heat-receiving areas via a heat spreader made of a heat-conductive material; an inlet hole and an outlet hole opened to the surface of the heat-radiating sheet and located at both ends of the circulating flow passage; a pump having a discharge port and a suction port that communicate with the inlet hole and the outlet hole, and installed on the heat-radiating sheet; and a radiator continuous with the circulating flow passage of the heat-radiating sheet.

This application claims benefit of Japanese Patent Application No. 2007-061507 filed on Mar. 12, 2007, which is hereby incorporated in its entirety by reference.

BACKGROUND

1. Field of the Invention

The present invention relates to a thin liquid cooling (water cooling) system, and particularly, to a liquid cooling system that is suitable to be used for a notebook computer having a plurality of heat-generating elements (heat-generating sources).

2. Description of the Related Art

Recent notebook computers have a plurality of heat-generating elements, such as a GPU and a chip set as well as a CPU. How to effectively cool the plurality of heat-generating elements becomes a technical object for the computers. Further, in a notebook computer in which the storage space for components is limited, as is shown, for example, in Japanese Unexamined Patent Application Publication Nos. 2005-166030, 2003-324174, 2002-94277, and the like, a liquid cooling system is needed that is thin and which is highly unitary property.

However, a conventional liquid cooling system needs tubes in order to connect elements to one another because a pump, a heat-absorbing unit, a heat-radiating unit (radiator), and the like are provided independently. Therefore, the system lacks in integrity (unit property), has a large amount of evaporation in coolant and has a problem even in assembling performance. Further, in a notebook computer in which a plurality of heat-generating elements exist, a heat-radiating structure that can radiate heat more efficiently is desired.

SUMMARY

A liquid cooling system includes a heat-radiating sheet having a pair of heat-conductive metal plates that are superimposed on each other, and having a circulating flow passage between the pair of heat-conductive metal plates. A plurality of heat-receiving areas are partitioned on the heat-radiating sheet. A plurality of heat-generating elements are installed on each of the heat-receiving areas via a heat spreader made of a heat-conductive material. An inlet hole and an outlet hole are opened to the surface of the heat-radiating sheet and located at both ends of the circulating flow passage. A pump has a discharge port and a suction port that communicate with the inlet hole and the outlet hole, and is installed on the heat-radiating sheet. A radiator continuous with the circulating flow passage of the heat-radiating sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view showing one embodiment of a liquid cooling system;

FIG. 2 is an exploded perspective view of a heat-radiating sheet of FIG. 1;

FIG. 3 is a plan view of FIG. 2.

FIG. 4 is a side view of FIG. 3;

FIG. 5 is a plan view of a piezoelectric pump as a single body;

FIG. 6 is a sectional view taken along a line VI-VI of FIG. 5;

FIG. 7 is a perspective view of a radiator as a single body;

FIG. 8 is a sectional view taken along a line VIII-VIII line of FIG. 7;

FIG. 9 is a sectional view taken along a line IX-IX of FIG. 7; and

FIG. 10 is a plan view of a flow passage plate as a single body that constitutes each flow passage unit of the radiator.

DESCRIPTION OF THE EMBODIMENTS

As shown in FIGS. 1 to 4, a liquid cooling system 100 of this embodiment includes, as its main components, a heat-radiating sheet 10, a piezoelectric pump 20, a radiator 40, and a cooling fan (sirocco fan) 50, and cools three heat-generating sources of a CPU 101, a GPU 102, and a chip set 103.

The heat-radiating sheet 10 is composed of a pair of heat-conductive metal plates 10U and 10L that are superimposed on each other, and three planar rectangular heat-receiving areas A, B, and C are set on the sheet 10 by facing slits (easily deformable portion) 10 a. On the face of the lower heat-conductive metal plate 10L opposite the upper heat-conductive substrate 10U, the CPU 101, GPU 102, and chip set 103 that are located on the heat-receiving areas A, B, and C, respectively, are mounted (contacted) via heat spreaders 101H, 102H, and 103H, respectively.

The heat-conductive metal plates 10U and 10L of the heat-radiating sheet 10 are preferably made of a metallic material that contains SUS, copper, or aluminum as its main constituent, and the lower heat-conductive metal plate 10L is formed with a flow passage recess 11 a that constitutes a circulating flow passage 11. The depth of the flow-passage recess 11 a is, for example, around 0.5 mm.

A flow passage cutoff protrusion 11 b is formed within the flow passage recess 11 a (circulating flow passage 11), and portions in front of or behind the flow passage cutoff protrusion 11 b constitute a flow passage starting end 11 c and a flow passage terminating end 11 d. The flow passage starting end 11 c communicates with a heat-absorbing outgoing flow passage 11 e that runs in order of the heat-receiving areas C, B, and A, a heat-absorbing folded-back flow passage 11 f, and a heat-absorbing incoming flow passage 11 g that runs in order of the heat-receiving areas A, B, and C, leads to an inflow end 11 h extending to the radiator 40, and is then connected with the flow passage terminating end 11 d from a discharge end 11 i extending from the radiator 40. Although the flow passages are drawn simply, they can be suitably made to meander so as to increase flow passage length.

In the heat-conductive metal plate 10U, an inlet projection (inlet hole) 12 and an outlet projection (outlet hole) 13 that communicates with the circulating flow passage 11 are formed so as to project in correspondence with the flow passage starting end 11 c and the flow passage terminating end 11 d, and an outlet projection (outlet hole) 14 and an inlet projection (inlet hole) 15 are formed in correspondence with the radiator inflow end 11 h and the radiator discharge end 11 i. The inlet projection 12 and the outlet projection 13 communicate with and fit into a discharge port (hole) 34 and a suction port (hole) 35 of the piezoelectric pump 20, respectively.

The piezoelectric pump 20 is set on the upper heat-conductive substrate 10U of the heat-radiating sheet 10. That is, the piezoelectric pump 20 is located on any one of the surface and back of the heat-radiating sheet 10, and the CPU 101, GPU 102, and the chip set 103 are located on the other face thereof. According to this arrangement, planar superimposition with a cooling fan can be permitted, cooling efficiency can be improved, and the planar size of the whole liquid cooling system 100 can be suppressed. Further, if the piezoelectric pump 20 and the radiator 40 are arranged on the lower side in FIG. 1, the pump can be provided on the same face as a heat source. Thus, the upper face of the liquid cooling system 100 can be made flat, and the liquid cooling system 100 can be efficiently arranged below a keyboard of, for example, a notebook computer.

Although the configuration of the pump (piezoelectric pump) 20 does not matter in the invention, the piezoelectric pump 20 of the embodiment will be described with reference to FIGS. 5 and 6. The piezoelectric pump 20 has a lower housing 21 and an upper housing 22 sequentially from below.

The discharge port 34 and the suction port 35 are bored in the lower housing 21 so as to be orthogonal to a plate thickness plane of the housing and parallel to each other. A piezoelectric vibrator (diaphragm) 28 is liquid-tightly sandwiched and supported between the upper housing 21 and the lower housing 22 via the O ring 29, and a pump chamber P is formed between the piezoelectric vibrator 28 and the lower housing 21. An atmospheric chamber P is formed between the piezoelectric vibrator 28 and the upper housing 22.

The piezoelectric vibrator 28 is a unimorph vibrator having a central shim 28 a, and a piezoelectric body 28 b stacked on one (upper face of FIG. 6) of the surface and back of the shim 28 a. The shim 28 a faces the pump chamber P and contacts liquid. The shim 28 a is made of a conductive metallic thin plate material, for example, a metallic thin plate having a thickness of about 50 to 300 μm and formed of stainless steel, a 42 alloy, or the like. The piezoelectric body 28 b is made of, for example PZT (Pb(Zr, Ti)O₃) having a thickness of about 300 μm, and is subjected to polarizing treatment in the direction of the surface and back thereof. Such a piezoelectric vibrator is widely known.

The discharge port 34 and suction port 35 of the lower housing 21 are respectively provided with check valves (umbrella) 32 and 33. The check valve 32 is a suction-side check valve that allows flow of fluid from the inlet port 35 to the pump chamber P, and does not allow flow of the fluid in a direction reverse thereto, and the check valve 33 is a discharge-side check valve that allows flow of the fluid from the pump chamber P to the outlet port 34, and does not allow flow of the fluid in a direction reverse thereto.

The check valves 32 and 33 have the same form, and are constructed by mounting umbrellas 32 b and 33 b made of an elastic material on perforated substrates 32 a and 33 a bonded and fixed to flow passages. Such check valves (umbrellas) themselves are widely known.

In the above piezoelectric pump 20, if the piezoelectric vibrator 28 elastically deform (vibrates) in a vertical direction in the direction of the diameter, the suction-side check valve 32 is opened and the discharge-side check valve 33 is closed, in a stroke where the volume of the pump chamber P increases. Therefore, liquid flows into the pump chamber P from the suction port 35 (outlet projection 13 of the heat-radiating sheet 10) (FIG. 7B). On the other hand, in a stroke where the volume of the pump chamber P reduces, the discharge-side check valve 33 is opened and the suction-side check valve 32 is closed. Therefore, the liquid flows out of the pump chamber P into the discharge port 34 (inlet projection 12 of the heat-radiating sheet 10). Accordingly, a pumping action is obtained by making the piezoelectric vibrator 28 continuously elastically deform (vibrate), and liquid flows through the heat-absorbing outgoing flow passage lie, heat-absorbing folded-back flow passage 11 f, and heat-absorbing incoming flow passage 11 g in the heat-receiving areas A, B, and C from the flow passage starting end 11 c of the circulating flow passage 11 of the heat-radiating sheet 10, thereby absorbing heat therefrom, then reaches the radiator inflow end 11 h, and then enters the radiator 40. The liquid that is circulated through the radiator 40 and has radiated heat is discharged to the radiator discharge end 11 i, and returns to the flow passage terminating end 11 d.

The radiator 40 is obtained by connecting the outlet projection (outlet hole) 14 and the inlet projection (inlet hole) 15 of the heat-radiating sheet 10 directly (without via a tube). As shown in FIGS. 7 to 9, the radiator 40 of this embodiment is composed of a plurality of stages of stacked flow passage units 41. The flow passage units 41 have the same structure except for an uppermost flow passage unit 41.

Each flow passage unit 41 is constituted by a pair of flow passage plates 42U and 42L that are superimposed on and coupled with each other. The flow passage plates 42U and 42L are constituted from, for example, press-molding articles made of a metallic material (brazing sheet) that is excellent in heat-conductivity, and have a symmetrical shape (the same single body shape) with respect to a superimposed face (stacked face). FIG. 10 shows a single body shape of the flow passage plate 42U (42L). The flow passage plate 42U (42L) has an elongated shape, and has a flat joining face 45 at a peripheral edge of a planar U-shaped flow passage recess 46. Both ends (ends opposite to the U-shaped folded-back portion) of the U-shaped flow passage recess 46 are formed with spacers 47S and 48S that protrude outward from portions of the U-shaped flow passage recesses 46, and an inlet hole 47 and an outlet hole 48 are bored in the spacers 47S and 48S, respectively.

The above-described flow passage plates 42U and 42L are superimposed on each other such that the flow passage recesses 46 face outward in directions opposite to each other, and their joining faces 45 are joined together by, for example, brazing. Then, a flat U-shaped coolant flow passage 11X is formed by the upper and lower U-shaped flow passage recesses 46 that protrudes in the directions opposite to each other. Further, the spacers 47S (48S) of the upper and lower flow passage units 41 abut on each other, whereby the inlet holes 47 of the upper and lower flow passage units 41 communicates, and the outlet holes 47 thereof communicate with each other. Between the superimposed flow passage units 41, a cooling air passage space S (FIG. 9) is formed. The inlet hole 47 (outlet hole 48) is not bored in the spacer 47S (48S) of the upper flow passage plate 42U of the uppermost flow passage unit 41.

The outlet projection (outlet hole) 14 and inlet projection (inlet hole) 15 that are formed in the heat-conductive metal plate 10U fit into the inlet hole 47 and outlet hole 48, respectively, of the lowermost flow passage unit 41, and a plurality of layers of radiator flow passages are formed from the radiator inflow end 11 h to the radiator discharge end 11 i.

The heat-radiating sheet 10 and the radiator 40 have a planar U-shaped space as a whole, and the cooling fan (sirocco fan) 50 is disposed within this U-shaped space. A blow-off direction W (FIG. 1, FIG. 3) of cooling wind of the cooling fan (sirocco fan) 50 turns to the radiator 40, and the cooling wind cool the liquid that passes through the spaces S between the flow passage units 41 and flows through the flow passage units 41. According to such planar arrangement, since the wind generated from the cooling fan 50 can be efficiently applied to the cooling system 100, space can be saved.

In the liquid cooling system 100 having the above configuration, the heat-receiving areas A, B, and C are defined on the single (made of a continuous metallic material) heat-radiating sheet 10, and the CPU 101 (heat sink 101H), the GPU 102 (heat sink 102H), and the chip set 103 (heat sink 103H) are mounted on the heat-receiving areas A, B, and C, respectively. Further, since the piezoelectric pump 20 and the radiator 40 are coupled together in the heat-radiating sheet 10, all circulating flow passages are formed without using a flexible tube. Since the heat-receiving areas A, B, and C is partitioned by the facing slits (easily deformable portions) 10 a, even if a height difference is between CPU 101 (heat sink 101H), the GPU 102 (heat sink 102H), and the chip set 103 (heat sink 103H), each heat-receiving area can be deformed flexibly so as to follow the height difference, and thermal coupling to the flat face of each heat-generating elements can be made easy.

The liquid discharged from the discharge port 34 of the piezoelectric pump 20 enters the circulating flow passage 11 (flow passage starting end 11 c) from the inlet projection 12 of the heat-conductive metal plate 10U, then flows through the heat-absorbing flow passage 11 e, 11 f, and 11 g in the heat-receiving areas A, B, and C, thereby absorbing heat from the CPU 101, the GPU 102, and the chipset 103, and then reaches the outlet projection 14 of the heat-radiating sheet 10 at the radiator inflow end 11h. After the liquid that has reached the outlet projection 14 enters the cooling flow passage 11X from the inlet hole 47 of each flow passage unit 41 of the radiator 40 and leaves the outlet hole 48, the liquid is discharged to the radiator discharge end 11 i from the inlet projection 15, and returns to the flow passage terminating end 11 d. The liquid that has reached the flow passage terminating end 11 d returns to the inside of the piezoelectric pump 20 from the inlet projection 12, and thereafter, repeats the same circulation. The liquid that passes through the cooling flow passage 11X within the radiator 40 is more sufficiently cooled by the cooling wind from the cooling fan (sirocco fan) 50.

In the above embodiment, easily deformable portions are formed in the heat-radiating sheet 10 by the facing slits (easily deformable portions) 10 a. However, the easily deformable portions may be formed by thin-walled portions. Further, in the illustrated example, the facing slits (easily deformable portions) 10 a are formed in both the heat-conductive metal plates 10U and 10L, the facing slits (easily deformable portions) 10 a may be formed only at one of them. 

1. A liquid cooling system comprising: a heat-radiating sheet having a pair of heat-conductive metal plates that are superimposed on each other, and having a circulating flow passage between the pair of heat-conductive metal plates; a plurality of heat-receiving areas partitioned on the heat-radiating sheet; a plurality of heat-generating elements installed on each of the heat-receiving areas via a heat spreader made of a heat-conductive material; an inlet hole and an outlet hole opened to the surface of the heat-radiating sheet and located at both ends of the circulating flow passage; a pump having a discharge port and a suction port that communicate with the inlet hole and the outlet hole, and installed on the heat-radiating sheet; and a radiator continuous with the circulating flow passage of the heat-radiating sheet.
 2. The liquid cooling systems according to claim 1, wherein the plurality of heat-receiving areas are partitioned via easily deformable portions formed in the heat-radiating sheet.
 3. The liquid cooling system according to claim 2, wherein the easily deformable portions are slits formed in at least one of the pair of heat-conductive metal plates that constitute the heat-radiating sheet.
 4. The liquid cooling system according to claim 1, wherein the heat-radiating sheet and the radiator defines a planar U-shaped space, and a fan that gives cooling air to the radiator is arranged in the U-shaped space.
 5. The liquid cooling system according to claim 1, wherein the heat-generating elements are located on any one of the surface and back of the heat-radiating sheet, and the pump is located on the other face thereof.
 6. The liquid cooling system according to claim 1, wherein the inlet hole and outlet hole of the circulating flow passage are formed as cylindrical projections in the heat-radiating sheet, and the discharge port and suction port of the pump are formed as a discharge port that communicates with the cylindrical projection serving as the inlet hole, and a suction port that communicates with the cylindrical projection serving as the outlet hole.
 7. The liquid cooling system according to claim 1, wherein the pump is a piezoelectric pump.
 8. The liquid cooling system according to claim 1, wherein the heat-generating elements include a CPU and a GPU of a notebook computer.
 9. The liquid cooling system of the claim 1, wherein the radiator has a plurality of stacked flow passage units, and each of the flow passage units includes the inlet hole and the outlet hole, and a cooling flow passage connecting the inlet hole and the outlet hole.
 10. The liquid cooling system according to claim 9, wherein each flow passage unit is formed by stacking and coupling a pair of flow passage plates that form a liquid flow passage that is bent into a U shape at least once, and the inlet hole and the outlet hole are bored in the pair of flow passage plates.
 11. The liquid cooling system according to claim 9, wherein the pair of flow passage plates that constitute each flow passage unit has a plane-symmetrical shape that is symmetrical with respect to superimposed faces, and have a flow passage recess that forms a planar U-shape, and the inlet hole and the outlet hole that are formed at one end and the other end of the flow passage recess. 